The present invention relates to a manufacturing apparatus for a sheet-shaped molding material, and more particularly, to an apparatus for manufacturing a sheet-shaped FRP (fibrous glass reinforced plastic) molding material by conveying between two resin-made films a blended and kneaded composition composed of a solid material such as glass fiber or the like and a liquid material such as resin or the like. The apparatus may be suitably used especially in the manufacturing of thick, wide molding compounds (hereinafter referred to as TMC) through equalization of the sheet material thickness in the widthwise direction.
Conventionally, an apparatus as shown in FIGS. 7 and 8 has been well known for manufacturing this type of sheet-shaped FRP molding material. Throughout the drawings, reference character A denotes glass fiber rovings, reference character B denotes a paste-like liquid material composed of resin components or the like, and reference characters C, C' denote films, such as polyethylene sheets. As a first step, the glass fiber rovings A are cut into chopped strands of a given length by a roving cutter 1. Then, the chopped strands are spread onto the liquid material b, which is fed onto mixing rollers 3, 3' for impregnation, from a pipe 2 which supplies the liquid material B. While passing between the rotating mixing rollers 3, 3' as shown, the liquid material b is impregnated into the chopped strands of the glass fiber A. The blended and kneaded composition which has been thus impregnated is scraped off by the scraping rollers 4, 4', which are placed beneath the mixing rollers 3, 3', so as to drop onto the lower film C disposed over the transport conveyer 5. A fixed amount of the blended and kneaded composition is conveyed between the upper film C' and the lower film C and is shaped by a shaping roller 6 into a sheet shaped product for transport at a later process.
When the blended and kneaded composition is made to fall onto the lower film C disposed over the conveyer 5 by the manufacturing apparatus, it does not fall in an equal amount along the width of the lower film C. That is, more will fall in the central portion, with less on both sides, like the distribution condition as shown with the broken lines in FIG. 6, especially when the vertical drop distance from the scraping rollers 4, 4' to the film C is large. Thus, the product provided is thicker at the central portion relative to the width of the sheet, and comparatively thinner at both side portions, with the result being that the resultant products cannot be made uniform in width and thickness.
According to experiments directed to a solution of the above-described problem, it is found that the blended and kneaded composition can be uniformly dropped along the width of the film C when the drop distance from the scraping rollers 4, 4' to the film C is made shorter, and the film C is arranged immediately under the scraping rollers 4, 4' as shown in FIG. 9. However, in this case, 5 to 10% of the blended and kneaded composition is scattered outside the system due to gaps present among the scraping rollers 4, 4' and the film C, thus resulting in more material loss and a polluted side wall.
Furthermore, in the conventional apparatus, when the liquid material B is fed into the rollers 3, 3' for impregnation, it is fed under pressure into the supply pipe 2 by a fixed pump 9 from a tank 8, as shown in FIG. 8. The liquid material B is then fed over the rollers 3, 3' from holes 2a, each having the same diameter and drilled at a given pitch along the length of the pipe 2. In this case, the pressure is higher within the pipe 2 at the portion of the pipe 2 closest the pump 9, and is lower at the other end of the pipe 2 resulting in unequal supply amounts of the liquid material B. That is, an equal amount of liquid material B is not fed across the entire apparatus in the axial direction. This uneven supply of the liquid material B interferes with the equalization of the thickness of the products to be manufactured.